1. Field of the Invention
The invention relates generally to specialized ventilation systems and more particularly to a ventilation system designed for use in conjunction with sewer vent pipes in cold climates.
2. Description of the Prior Art
A serious problem experienced by home owners in the cold weather regions of the world is that of frost accumulation in sewer vent pipes. The problem is caused by the use of ambient and warm water in routine daily living in areas where the air temperature remains well below freezing for days and weeks at a time. In order to properly plumb a home or commercial building for sewer there must be an air equalizing vent. Typically, when water is disposed of in the normal sewer system the water flows down and draws air in the vent to replace the air displaced by the water. When the water reaches the lateral lines some air moves in the reverse direction carrying with it among other things moisture and steam from the ambient and warm water discarded. When this air reaches the exposed portion of the stack, above the roof, in cold weather it will form frost on the inside of the stack. After a period of time the frost can build up and block the vent thereby preventing the ingress of air when using the system. In order to replace the air displaced by the water a vacuum will be created and suck the water from the traps in the building in order to allow air to enter the system. When the air reverses direction, with the vent blocked, the moisture laden air with sewer gases will enter the building, endangering the occupants of the building. In this respect, there have been a number of instances where sewer gas accumulation within a residence has resulted in the death of one or more of its occupants. In addition, many injuries have resulted where people have fallen from roofs while trying to thaw out their sewer vent pipes.
There are many examples of vent pipe covers as shown in the following U.S. Patents: U.S. Pat. No. 4,206,692 issued Jun. 10, 1980 to Johnston and U.S. Pat. No. 4,399,743 issued Aug. 23, 1983 to Izzi, Sr. U.S. Pat. No. 4,442,643 issued Apr. 17, 1984 to Stadheim recognizes the problem of cold weather frost build up but solves it by insulating the pipe above the roof line. U.S. Pat. No. 5,081,914 issued Jan. 21, 1992 to Mejia is another example of a roof vent cap and U.S. Pat. No. 5,245,804 issued Sep. 21, 1993 to Schiedegger et al. disclose a vent pipe shield.
As known to Applicant the prior art is devoid of methods and means for inhibiting the build up of frost on the sewer vent pipe in cold weather except by adding an insulated sleeve to the outside of the pipe as shown by Stadheim.